Topping Mangel Wurzels

Does it harm the mangel wurzels if their tops ore cut off once a month?

Removing leaves will decrease the size and harden the tissues of the
beet root. If you wish to grow the plant for the top, the root will
continue to put out leaves for you for a time; if you grow it for the
size and quality of the root, you need all the leaf-action you can get,
therefore do not reduce the foliage.